Yes, I was going to say, "Didn't they make a movie about this"? And advertised it as the "true" version of the Arthur story, even though it's just about as fictional as any other.

But yes, some 5500 Iazyges (a Sarmatian tribe) were sent to northern Britain to defend the border against the Picts and, as far as I know, over time became integrated into the local population.

I'm not sure that I'd call Central Asia (or Eastern Europe, for that matter) the Middle East, though. However, the Sarmatians were closely related, at least by language, to the Iranians, and Iran is generally regarded as part of the Middle East.